Method#to_proc Procs have "sticky" bindings
Please see the attached sample script (or view the gist at https://gist.github.com/1197634).
It would appear that a Proc object that is obtained via Method#to_proc behaves unlike other Procs when used with instance_exec. I'm not entirely sure that this is a bug so much as a gap in documentation, but I found it interesting, in either case, to note the subtle difference.
A Proc object created by Method#to_proc doesn't actually allow instance_exec to modify "self" for the block. Sample output is provided in the comments of the attached script.
Thanks in advance!